It has been known that barium zirconate (BaZrO3) has a low reactivity with yttrium-barium-copper oxides (e.g., Y1Ba2Cu3Ox generally shown as YBCO). For this reason, single crystals of YBCO have often been grown in BaZrO3-coated crucibles. Detailed studies of the reactivity have shown that certain reaction by-products, such as YBa2ZrO6 and BaZr1−xCuxOy, can form. Further references have described addition of BaZrO3 particles of about 100 nm in size to bulk melt-processed YBCO, but the BaZrO3 was found to agglomerate at the growth front of the grains and seeded YBCO grains, leading to multigrain growth (see Luo et al., J. Supercon. 13(4), pp. 575-581 (2000)).
Other instances of BaZrO3 with superconductive structures are known. For example, U.S. Pat. Nos. 6,077,304 and 6,235,402 by Goyal et al. describe use of barium zirconate as a buffer layer on a lanthanum aluminate layer on a nickel base substrate. Such layers are deposited by sol-gel techniques. U.S. Pat. Nos. 5,508,255 and 6,074,990 also describe barium zirconate as a buffer layer. U.S. Pat. Nos. 5,089,455 and 5,814,262 describe reaction of YBCO on a zirconia substrate to form a thin layer of barium zirconate at the interface. However, in none of the previous work has BaZrO3 been known or used to form pinning centers for superconductive thin film structures, especially a thin film YBCO structure. Other barium oxides including a group 4 or group 5 metal such as cerium and the like may be employed as well.